Production of  cement can  be  increased by increase  of  extraction of  natural resources and  construction of  new  plants  for  processing these natural resources. However, this is a costly and environmentally detrimental method.

At the same time, waste of ferrous metallurgy contains an enormous amount of oxidized steel slags with a high basicity.

After  meltdown of  such  slags  in the  smelting  unit  MAGMA and partial reduction by carbon of oxides contained in them by process route  shown  below (Fig. 4), we get molten  slag (molten clinker) similar by its chemical composition to cement clinker manufactured by conventional methods at existing cement plants (Table 1 below).

Chemical composition of oxidized steel slag, cement clinker and Portland cement type СЕМ1-

Table 1

Material	content, %
	Cao	Al2o3	Sio2	Mgo	Fe2o3	Mno	Fe, prills	So3
Oxidized steel slag	40-55	1.5-3	15-19	1.5-2.5	18-25	4-7	4-6	—
Slag smelted and partially reduced in MAGMA	61.7-63	1.8-3.7	18-24	1.8-3.1	4.5-5.2	2.5-4	0	—
Conventional cement clinker	60-67	3-8	17-25	2.5-5	4-5	—	0	—
Typical Portland cement type СЕМ  1	62-64	5.5	21.5	1.5	3-4	—	0	1.9

Production capacity of MAGMA for clinker is 200,000-400,000 tons per year and depends on chemical composition and the temperature of the slag being processed.

Up to 800 kg of melted cement clinker and up 250 kg of iron alloy can be produced out of 1 ton of re-smelted steel slag.This allows to significantly reducing the costs of production of the melted clinker.

Production of melted cement clinker out of ferrous metallurgy waste allows decreasing the environmental impact due to refusal from the use of natural resources, reducing energy intensity of production and CO2 emissions per ton of products, i.e., achieve a significant environmental improvement (Flow diagram & Table 2 below).

Conventional method of Clinker production 

1. Pit (Limestone, clay)
2. Transport
3. Crushing
4. Pre-homogenizing
5. Grinding
6. Gas purification
7. Preliminary roasting
8. Rotary kiln
9. Cooling 

Production of Portland cement 

10. Warehouse of clinker
11. Additives
12. Grinding of Portland Cement
13. Cement silo, shipment

 Production of Melted clinker 

14. Slag dump
15. Transport
16. Warehouse, charge heating
17. MAGMA Unit
18. Granulator
19. Gas purification
20. Oxygen Station

 Comparative figures of cement clinker production methods-

Table 2

Production method	Raw materials	Saleable products	Energy carriers used	Specific units per 1 ton of product
				Limestone consumption	Natural gas consumption	Coal consumption	Off-gases volume	СО2 emissions
				kg	m3	kg	kg	kg
Conventional method	Natural resources (clay, limestone)	Cement clinker	Natural gas, electric power	1150-1850	82-96	—	1500-1700	720-840
MAGMA method (range of given figures depends on slag composition)	Ferrous metallurgy waste (oxidized steel slags, scales, gas treatment dust)	Cement clinker, iron alloy	Natural gas, electric power, coal	50-570	60-70	70-110	520-930	290-615

PROCESSING OF SLAGS OF NON-FERROUS METALLURGY

Leading  scientific  centers of  Russia  conducted  researches that showed efficiency of  use  of  liquid slags  for  production of  cast  slag products: parts   of  tunnel   lining,  weighting material   for  pipe-lines, products for chemical, metallurgical and construction industries.

Best quality is achieved in slag castings made out of low basicity (acidic slags) with high content of iron oxides (Table 3).

Such chemical compositions are characteristic of the slags from non-ferrous metallurgical plants that produce nickel and copper and for the slags of thermal power stations that work on thermal brown coal (Table 4).

Properties of cast slag products –                                                                                  Table 3

Parameter	Unit	Value
Volume weight	kg/m3	2900-3000
Ultimate compression strength	Mpa	200-500
Ultimate bending strength	Mpa	15-50
Impact strength	kJ/m2	1.06-1.25
Elasticity modulus	Mpa	(0.43-1.01)∙105
Poisson number	—	0.25
Thermal resistance	0c	200-600
Thermal conductivity at 20°C	W/(m∙0c)	1.07-1.52
specific heat capacity at 20°C	kJ/(kg∙0c)	0.67-0.85
Temperature coefficient of linear expansion within interval 20-600°C	0	-5
Abrasion coefficient	kg/m2	0.1-0.2
Water absorption	%	0.03-0.1
Freeze resistance	cycles	over 300
Acid resistance in 20% hydrochloric acid	%	upto 97.8
Acid resistance in concentrated sulphuric acid	%	up to 99.7
Alkali resistance in 35%alkali	%	up to 98.6
Diffusion coefficient of sr and cs ions: -att=25°C -att=600°C	cm2/s	~10-18 ~10-14

Average compositions of slags from non- ferrous metallurgy and thermal power plants-                                                                                                                 Table 4

Type of slag	Content, %											Melting temperature,°C
	Sio2	FeO	CaO	Al2o3	Mgo	Cu	Co	Ni	Zn	Pb	S
Copper smelter slags	32-45	25-45	12	3.2-9.7	2-11	0.3-0.9	—	—	0.5-1	0.22-0.8	0.4-1.2	1100-1150
Nickel shaft furnace slags	39-45	16-24	12-21	4.5-7.5	9-17	—	0.010- 0.024	0.1-0.17	—	—	0.43- 0.5	1100-1200
Nickel basic oxygen furnace slags	25-35	40-60	2-3	3-10	2-4	0.1-0.2	0.01- 0.02	0.3-0.7	—	—	2-3	1100-1200
Ash of thermal power plants working on brown coal	54-55	2.5-10	1.6-2.5	24.7-25.2	2.5-2.6	—	—	—	—	—	0.1-0.3	1400
Average composition of slag castings	44-49	7-20	6-16	9-20	5-13	—	—	—	—	—	—	1300-1350

 

These waste, which have relatively low melting temperature, are annually produced in large amounts and are accumulated in dumps.

MAGMA  allows   to   economically   smelt   slags   of   non-ferrous metallurgy and  thermal power   plants   with  adjustment of  chemical composition and  temperature of  molten  mass  in the  process  of  re- smelting.

Furthermore, the metal component present in slags of non-ferrous metallurgy is extracted from it and is used as additional saleable product.

The gas treatment system of the unit can capture zinc and lead contained in the slags being re-smelted.

As a result, production costs of slag castings can be significantly reduced through the sale of additionally produced metal.

MAGMA has better technical performance than slag-smelting units conventionally operated in the industry (Table 5).

MAGMA has still more  effective performance in case of using hot liquid  slags  fed  into  the  smelting  chamber of  the  unit  directly  from metallurgical furnaces.

In this case,the unit will be also used for leaning of slags of non- ferrous metallurgy.

Comparison of performance of slag-smelting units –

Table 5

Type of slag-smelting unit	Production capacity for smelted charge	Fuel consumption per 1 ton of charge		Consumption of blowing  per 1 ton of charge	Temperature of slag
	Tons/hour	Absolute units	MJ	m3	°C
Smelting unit MAGMA	up to 50	natural gas 70-82 m3	2600-3000	oxygen 157-182	1400-1650
Arc stationary furnace with water cooling of the unit body (limestone-alumina slag)	2.5 – 3	electric power 1500 kWh	5400	—	1650-1700
Regenerative tank furnace for production of mineral molten mass	3	natural gas 200 m3	7340	air 3700	1380

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